This disclosure relates to a metal hydroxy carbonate nanoparticle-coated phosphor and a method for preparing the phosphor. This disclosure further relates to a phosphor whose surface is coated with metal hydroxy carbonate nanoparticles, that is capable of maintaining a luminance for a long period of time when it is applied to a lamp, and a method for preparing the phosphor.
Luminescence is defined as a phenomenon in which a material absorbs an external energy to emit visible light. In a broad sense, a material causing this phenomenon is defined as a “phosphor”. The phosphor is used in various displays including fluorescent lamps, cathode ray tubes (CRTs), light emitting diodes (LEDs), plasma display panels (PDPs), vacuum fluorescent displays (VFDs), field emission displays (FEDs), and electroluminescence displays (ELDs). In addition, the phosphor directly affects the efficiency of products using phosphors.
In view of phosphor lifespan, a number of studies directed to phosphor efficiency have been conducted in a variety of application fields.
Since the phosphor efficiency and lifespan directly affects the efficiency of products using phosphors, there is a continuous demand for phosphors capable of maintaining luminance for a long period of time and preparation methods of such phosphors.
For example, various approaches have been attempted to maintain luminance of phosphors in three-wavelength lamps employing a mixture of red, green and blue phosphors in a predetermined ratio and in fluorescent lamps utilized in a variety of lighting units. In particular, a green BaMgAl10O17:Eu,Mn phosphor is used to manufacture fluorescent films, such as plasma display panels (PDPs), owing to its suitable optical efficiencies and excellent color purity. In order to maintain the luminance of this phosphor, coating the phosphor with a desired material has been proposed. The BaMgAl10O17:Eu,Mn phosphor shows considerable deterioration in luminance due to internal structural instability, defects to the phosphor surface which results from permeation of a short wavelength of ultraviolet light (185 nm) upon application to lamps, and formation of mercury compounds (e.g., Hg—O) caused by permeation of mercury ions. Conventional methods to solve these problems are mostly associated with coating phosphors with metal oxide to inhibit formation of mercury compounds when the phosphors are applied to lamps. However, the conventional methods have problems in that it has been difficult to obtain uniformly coated particles, and the coating process involves a heating process that causes deterioration of initial luminance. Another problem associated with these methods is that coated particles may unexpectedly inhibit light-emission.